1. Field of the Invention
The invention relates to a valving system for a hurricane plug, including a tubular body mounting a safety valve, a running tool and a retrieving tool.
2. Summary of the Prior Art
Hurricane plugs have long been known in the well drilling industry. When drilling a subsea well from a drilling vessel or barge, an impending storm necessitates that the vessel or barge be disconnected from the well and the well sealed shut until the storm has passed. Many times there is not sufficient advance warning of a storm to permit the drilling tool string to be removed from the well. In such cases, a hurricane plug, which is the equivalent of a packer, is secured to the top end of the drilling string and lowered into the well by a running tool. A valving system must be concurrently inserted in the well to prevent fluid flow upwardly out of the well when the running tool is disconnected from the hurricane plug after the setting of the hurricane plug is accomplished.
It is very important that the running tool not be withdrawn from the hurricane plug until the hurricane plug is set because the entire drilling string could be blown out of the well by pressurized well fluids existing below the hurricane plug.
It is equally important in the retrieval of the hurricane plug that the safety valve be opened as part of the retrieval operation so as to equalize pressures above and below the safety valve.
For this reason, a valving system, including a safety valve, special running tool and a special retrieval tool capable of performing all of the aforementioned operations in a thoroughly reliable manner, is a highly desired improvement in the well drilling art.